Structure and dielectric properties of electrochemically grown ZrO2 films.

The dielectric properties of electrochemically grown zirconium oxide films by anodisation of zirconium in 1.0 mol dm-3 phosphoric acid solution were investigated in a 3 to 30 V potential range with a view to inducing surface modifications for eventual use in biomedical and electronic applications. The oxide films grown at different potentials were characterised by Atomic Force Microscopy, X-ray photoelectron and Raman spectroscopies; the latter demonstrated the incorporation of phosphate ions into the passive films. Flat band potentials calculated from the Mott-Shottky analysis of the oxides semiconducting properties confirm the bilayer structure of the films. The oxide dielectric permittivity was evaluated from impedance spectroscopy measurements and the film oxide model proposed gave values independent of the oxide growth potential.

Can anodised zirconium implants stimulate bone formation? Preliminary study in rat model.

The mechanical properties and good biocompatibility of zirconium and some of its alloys make these materials good candidates for biomedical applications. The attractive in vivo performance of zirconium is mainly due to the presence of a protective oxide layer. In this preliminary study, the surface of pure zirconium modified by anodisation in acidic media at low potentials to enhance its barrier protection given by the oxides and osseointegration. Bare, commercially pure zirconium cylinders were compared to samples anodised at 30 V through electrochemical tests and scanning electron microscopy (SEM). For both conditions, in vivo tests were performed in a rat tibial osteotomy model. The histological features and fluorochrome-labelling changes of newly bone formed around the implants were evaluated on the non-decalcified sections 63 days after surgery. Electrochemical tests and SEM images show that the anodisation treatment increases the barrier effect over the material and the in vivo tests show continuous newly formed bone around the implant with a different amount of osteocytes in their lacunae depending on the region. There was no significant change in bone thickness around either kind of implant but the anodised samples had a significantly higher mineral apposition, suggesting that the anodisation treatment stimulates and assists the osseointegration process. We conclude that anodisation treatment at 30 V can stimulate the implant fixation in a rat model, making zirconium a strong candidate material for permanent implants.

The issue of corrosion in dental implants: a review.

Pure titanium or titanium alloys, and to a lesser extent, zirconium, are metals that are often used in direct contact with host tissues. These metallic biomaterials are highly reactive, and on exposure to fluid media or air, quickly develop a layer of titanium dioxide (TiO2) or zirconium dioxide (ZrO2). This layer of dioxide forms a boundary at the interface between the biological medium and the metal structure, determining the degree of biocompatibility and the biological response of the implant. Corrosion is the deterioration a metal undergoes as a result of the surrounding medium (electrochemical attack), which causes the release of ions into the microenvironment. No metal or alloy is entirely inert in vivo. Corrosion phenomena at the interlace are particularly important in the evolution of both dental and orthopedic implants and one of the possible causes of implant failure after initial success. This paper comprises a review of literature and presents results of our laboratory experiments related to the study of corrosion, with special emphasis on dental implants. In situ degradation of a metallic implant is undesirable because it alters the structural integrity of the implant. The issue of corrosion is not limited to a local problem because the particles pmduced as a result could migrate to distant sites, whose evolution would require further studies.

Susceptibilidad a la corrosión de diferentes aleaciones de uso odontológico / Susceptibility to corrosion of different alloys used in dentistry

Se ha estudiado la susceptibilidad a la corrosión en saliva artificial, de diferentes aleaciones no nobles de uso odontológico (Co-Cr, Ni-Cr y Cu-Al). Las aleaciones Cu-Al presentan una zona de pasividad con corrientes del orden de los 10ma.cm-2 y de una extensión que, dependiendo del tipo de aleación, va desde los 0,4 hasta 0,7 volts. Luego del potencial de ruptura, se produce la disolución selectiva del aluminio. Las aleaciones Ni-Cr presentan una corriente de pasividad del orden de los 0,5ma.cm-2, la zona pasiva tiene una extensión de 0,3 a 0,5 volts y posteriormente la aleación sufre picado. Finalmente, la aleación Co-Cr, si bien no presenta una neta zona pasiva, las corrientes no superan los 10ma.cm-2 durante más de 1,0 volts de barrido de potencial y no presenta corrosión localizada. Los resultados obtenidos muestran que, de las aleaciones ensayadas, y desde el punto de vista de su susceptibilidad a la corrosión, la aleación Co-Cr es la que presenta mejores características para su aplicación en la construcción de prótesis fijas (AU)

Susceptibilidad a la corrosión de diferentes aleaciones de uso odontológico / Susceptibility to corrosion of different alloys used in dentistry

Se ha estudiado la susceptibilidad a la corrosión en saliva artificial, de diferentes aleaciones no nobles de uso odontológico (Co-Cr, Ni-Cr y Cu-Al). Las aleaciones Cu-Al presentan una zona de pasividad con corrientes del orden de los 10ma.cm-2 y de una extensión que, dependiendo del tipo de aleación, va desde los 0,4 hasta 0,7 volts. Luego del potencial de ruptura, se produce la disolución selectiva del aluminio. Las aleaciones Ni-Cr presentan una corriente de pasividad del orden de los 0,5ma.cm-2, la zona pasiva tiene una extensión de 0,3 a 0,5 volts y posteriormente la aleación sufre picado. Finalmente, la aleación Co-Cr, si bien no presenta una neta zona pasiva, las corrientes no superan los 10ma.cm-2 durante más de 1,0 volts de barrido de potencial y no presenta corrosión localizada. Los resultados obtenidos muestran que, de las aleaciones ensayadas, y desde el punto de vista de su susceptibilidad a la corrosión, la aleación Co-Cr es la que presenta mejores características para su aplicación en la construcción de prótesis fijas